Formation reduction in pressure coking equipment

ABSTRACT

Formation of mineral type scale in pressure coking equipment used in coking waste materials in the liquid phase is eliminated by effecting the coking of such materials using direct countercurrent heat exchange with a hot hydrocarbon stream which is kept continuously circulating along the walls of the equipment.

United States Patent Hess et al. 1 Dec. 17, 1974 [5 FORMATION REDUCTION IN PRESSURE 3,181,600 5/1965 Woodward et a1. 203/100 COKING EQUIPMENT 3,392,089 7/1968 Guptill et al 203/100 Inventors: Howard V. Hess, Glenham; William F. Franz, Gardiner; Edward L. Cole, Fishkill, all of N.Y.

Filed:

Assignee: Texaco Inc., New York, N. Y

Jan. 15, 1973 Appl. No.: 323,554

U.S. c1 201/2.s, 201/10, 201/25 Int. Cl ClOb 43/14 Field of Search 48/211, 197 A; 110/8 C;

References Cited UNITED STATES PATENTS Hess et a1. 162/30 Primary Examiner-Samih N. Zaharna Assistant ExaminerPeter A. Hruskoci Attorney, Agent, or Firm-T. H. Whaley; C. G. Ries 5 7 ABSTRACT 7 Claims, 1 Drawing Figure 001.0 lo HYDROCARBON AQUEOUS WASTE STREAM 'Tf commuous HYDROCARBON PHASE r 6 -s0oF M commuous r WATER PHASE 5 l COLD I uoum AQUEOUS DEWATER'NG EFFLUENT -SLURRY co e MINERAL SCALE PAIENTED DEBI 7 I974 AQUEOUS WASTE STREAM CONTINUOUS HYDROCARBON PHASE CONTINUOUS WATER /7/ PHASE GAS COLD AQUEOUS HYDROCARBON SLURRY DEWATERING LIQUID EFFLUENT COKE MINERAL SCALE FORMATION REDUCTION IN PRESSURE COKING EQUIPMENT BACKGROUND OF THE INVENTION are coked. The mineral scale materials are precipitated but do not stick to the walls of the vessel which remain wet with hydrocarbon. The aqueous phase and coke and mineral scale particles are allowed to coalesce at This invention is concerned with an improvement in 5 the interface 3 and then pass as a continuous aqueous the coking of wast m terial i th li id phase slurry through the trap-tray 4. The bottom of the tower h b Scale formation on h pressure ki i is filled now with a continuous aqueous phase containm d i li i d ing suspended coke and mineral scale particles. Cold In commonly assigned U.S Pat. No. 3,507,788 issued hydrocarbon from the p of tower 2 is Passed thmugh Apr. 21, 1970 there is disclosed a process for treating [me 5 through sparger 12 and droplets of hydmcm' aqueous wastes by coking Same in the absence f added bon are heated as they pass through the hot aqueous free Oxygen at a temperature of 0 to 750%; under phase; are finally collected at the trap tray and routed a pressure of about 300 to 3000 psig for a time ranging through the heater 6 where any makeup heat for the from about minutes to 6 houm process IS supplied. The cold aqueous slurry from the The above outlined process and subsequent varia- 15 bottom of the tower r to produce an aqua" dons thereof Covered by a number of commonly ous effluent, coke and mineral scale. The aqueous efsigned patents are carried out in pressure coking equipfluent now greatly rduced and BOD can be ment. With experience it has been found that a large further by Plologlcal p i or carbon abportion of the real cost of such equipment is due to P f to recevmg waters' The maintenance problems arising during use, and, in par- 12 mm the ewatffirmsstep may e used as landfill ticular, to the formation of scale in the heat exchangers or to [ts eat associated with the equipment Gas, largely CO IS produced in the process. Should The main object of this invention therefor is to th s gas contain ob ectionable materials such as H 8, it vide a modified process wherein such scale formation be burned the fired h r 6 to pr0du ce the rela' is eliminated tively less noxious SO .wh1ch 1s vented with flue gas This object is achieved in accordance with the presfromfired heater ent invention by using direct countercurrent heat ex- Thls procetss apphcable to waste Streams in Change between the f d to be coked and a hot hydro waste materials are largely from carbohydrate origin Carbon stream and thus are amenable of coklng at temperatures in the range of 450650F. Examples of wastes treated by DESCRIPTION OF DRAWINGS liquid phase coking are shown in Table I below. These This and other related objects of the present invenwastes were coked. at 550F. and 1000 psig in the liquid tion will become apparent as the description thereof phase.

Liquid Liquid COD Dry Coke Ash Wt. Waste Char e Efilucnt Removal Yield Wt. 7rdry 1 Charges CO COD* '7: 70 of charge coke Raw sewage 9.2 84.7 2.0 36.0 sludge Biological 67 l3.9 79.0 2.5 51.6 sludge Spent sulfite 215 16.0 93.0 9.4 8.0 wood pulping liquid Spent kruft l67 24.0 86.0 5.2 8.5 wood pulping liquor Simulated 34 l0.3- 69.0 0.9 1.0

otato waste imulated I22 27.0 78.0 4.1 2.5 orange waste whey liquid 57 12.4 78.0 2.0 0.6

COD in grams (l /liter.

proceeds particularly when taken together with the accompanying drawing the single FIGURE of which is a flow diagram showing a simple arrangement for performing the process of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS In each of the runs represented in the above table the measure of scale mixed with coke was noted.

Normally liquid hydrocarbons are generally suitable for use in the process of this invention. Hydrocarbons and mixtures of hydrocarbons containing from 6 to 30 carbon atoms per molecule may be used, with hydrocarbons of 6 to 12 carbon atoms being preferred. Various petroleum fractions including kerosine, naphtha, odorless spirits gasoline, lubricating oil, alkylation bottoms", i.e. the bottoms fractions obtained from the alkylation of isobutane with butylenes and or propylene, C C aromatic hydrocarbons, e.g., aromatic hydrocarbons obtained by alkylation of benzene or toluene with propylene, Udex extract, i.e. an aromatic hyrocarbon fraction obtained from petroleum naphtha clohexane, dimethylcyclohexane, ethylcyclohexane,

tetralin, isopropylcyclohexane, cyclohexene, pinene, etc. and aromatic hydrocarbons, e.g. benzene, toluene, whens.xxlsnsstnsmmhthslsnatste a The preferred organic liquids are those which remain stable under waste coking conditions of 400 to 750F. and pressures of 300 to 3000 psig.

What is claimed:

1. In a process for preventing the formation of scale on the walls of a pressure coking tower used for coking cokable aqueous waste materials in the liquid phase, the steps of:

passing relatively cool aqueous waste into direct counter-current contact with a relatively hot liquid hydrocarbon in the upper part of said coking tower whereby said hydrocarbon portion is cooled and said aqueous waste is heated at a temperature of 400 to 750F under a pressure of 300 to 3500 psig to coke cokable materials in said waste and to precipitate scale to form a dispersed aqueous slurry, flowing the aqueous slurry downwardly into the lower part of said tower, withdrawing at least a part of said cooled hydrocarbon from the upper part of said tower and passing the same in direct countercurrent contact with said downwardly flowing aqueous slurry in said lower part of said tower thereby cooling said slurry, withdrawing said slurry including said scale from the lower part of said tower. and withdrawing cooled hydrocarbon liquid which has contacted said slurry from the lower part of said tower, the passage of the liquid hydrocarbon in said upper and lower parts of said tower being effective to wet the walls of said tower and prevent scale from adhering thereto. I 2. The process according to claim 1 wherein said hydrocarbon is maintained as a continuous phase. I

3. The process according to claim 1, wherein products are withdrawn as a slurry and dewatered to separate coke and mineral scale from a liquid effluent having reduced COD and BOD as compared with those of the aqueous waste.

4. The process according to claim 1 wherein said aqueous waste is sparged into the upper part of said tower and said hydrocarbon is sparged into lower part of said tower.

5. The. process of claim 4 wherein the cooled hydrocarbon that is withdrawn from the lower part of said tower is heated by external means and then reintroduced into said upper part of said tower.

6. The process of claim 1 wherein said hydrocarbon consists of petroleum fractions which remain stable under waste coking conditions of 400 to 750F. and

pressures of 300 to 3000 psig. selected from the group of kerosine, naphtha, odorless spirits gasoline, lubricating oil, bottoms fractions obtained from the alkylation of isobutane with butylenes and/or propylene, C -C aromatic hydrocarbons, Udex extract and mixtures thereof.

7. The process of claim 1 wherein said hydrocarbon is hexane, 2,3-dimethylbutane, heptane, octane, isooctane, nonane, decane, propylene tetramer, hexadecane, 2-methyl-l-pentene, methylcyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, tetralin, isopropylcyclohexane, cyclohexene, pinene', benzene, toluene, cumene, xylene,

methylnaphthalene and mixtures thereof. 

1. IN A PROCESS FOR PREVENTING THE FORMATION OF SCALE ON THE WALLS OF A PRESSURE COKING TOWER USED FOR COKING COKABLE AQUEOUS WASTE MATERIALS IN THE LIQUID PHASE, THE STEPS OF: PASSING RELATIVELY COOL AQUEOUS WASTE INTO DIRECT COUNTERCURRENT CONTACT WITH A RELATIVELY HOT LIQUID HYDROCARBON IN THE UPPER PART OF SAID COKING TOWER WHEREBY SAID HYDROCARBON PORTION IS COOLED AND SAID AQUEOUS WASTE IS HEATED AT A TEMPERATURE OF 400* TO 750*F UNDER A PRESSURE OF 300 TO 3500 PSIG TO COKE COKABLE MATERIALS IN SAID WASTE AND TO PRECIPITATE SCALE FROM A DISPERSED AQUEOUS SLURRY, FLOWING THE AQUEOUS SLURRY DOWNWARDLY INTO THE LOWER PART OF SAID TOWER, WITHDRAWING AT LEAST A PART OF SAID COOLED HYDROCARBON FROM THE UPPER PART OF SAID TOWER AND PASSING THE SAME IN DIRECT COUNTER-CURRENT CONTACT WITH SAID DOWNWARDLY FLOWING AQUEOUS SLURRY IN SAID LOWER PART OF SAID TOWER THEREBY COOLING SAID SLURRY, WITHDRAWING SAID SLURRY INCLUDING SAID SCALE FROM THE LOWER PART OF SAID TOWER, AND WITHDRAWING COOLED HYDROCARBON LIQUID WHICH HAS CONTACTED SAID SLURRY FROM THE LOWER PART OF SSAID TOWER, THE PASSAGE OF THE LIQUID HYDROCARBON IN SAID UPPER AND LOWER PARTS OF SAID TOWER BEING
 2. The process according to claim 1 wherein said hydrocarbon is maintained as a continuous phase.
 3. The process according to claim 1, wherein products are withdrawn as a slurry and dewatered to separate coke and mineral scale from a liquid effluent having reduced COD and BOD as compared with those of the aqueous waste.
 4. The process according to claim 1 wherein said aqueous waste is sparged into the upper part of said tower and said hydrocarbon is sparged into lower part of said tower.
 5. The process of claim 4 wherein the cooled hydrocarbon that is withdrawn from the lower part of said tower is heated by external means and then reintroduced into said upper part of said tower.
 6. The process of claim 1 wherein said hydrocarbon consists of petroleum fractions which remain stable under waste coking conditions of 400* to 750*F. and pressures of 300 to 3000 psig. selected from the group of kerosine, naphtha, odorless spirits gasoline, lubricating oil, bottoms fractions obtained from the alkylation of isobutane with butylenes and/or propylene, C9-C10 aromatic hydrocarbons, Udex extract and mixtures thereof.
 7. The process of claim 1 wherein said hydrocarbon is hexane, 2, 3-dimethylbutane, heptane, octane, isooctane, nonane, decane, propylene tetramer, hexadecane, 2-methyl-1-pentene, methylcyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, tetralin, isopropylcyclohexane, cyclohexene, pinene, benzene, toluene, cumene, xylene, methylnaphthalene and mixtures thereof. 